Several types of press-fit techniques for mounting electrically-conductive contact members such as pins into the preformed typically plated-through or blind holes in a PCB are known. In the most common type, a solid pin is used, which has no spring energy. The solid pin is press-fitted into the non-elastically-deformable area of a plated-through or blind hole, and relies on an enlarged pin section, the so-called star, whose widest dimension (across a diagonal) exceeds the inside diameter of the hole typically by about 0.004 inches. For example, for a solid pin with a nominal diameter of 0.025 inches, the hole size would be 0.029 inches .+-.0.002 inches and the star diameter would be 0.033 inches. In addition to its use in PCBs, as board to board or cable to board interconnects, as jumper shunt posts, as test posts, or as wire-wrap posts, such pins are also widely used in pin headers in which the header substrate is elastically-deformable. It is common to manufacture such pins as parts of a continuous strip wound upon a reel for use in automatic insertion machines. Reference is made to U.S. Pat. No. 4,318,964, which describes one way of making such pin strips and using such strips in automatic insertion machines, and U.S. Pat. No. 4,832,622, which describes one way of making pin headers using such pins, whose contents are herein incorporated by reference.
U.S. Pat. No. 4,3187,964 describes the configuration of contact pins, their assembly into a strip that can be reeled up, and a machine using the reel of pins for separating a pin from the strip and inserting it into a substrate such as a printed circuit board (PCB). That patent also describes a so-called star configuration in which a region along the length of the pin is enlarged to enhance its holding power in the substrate, commonly defined as the pull-off strength, i.e., the amount of force in grams needed to pull the pin out from the substrate.
Reference is also made to a paper by Irwin Zahn entitled "Six (6) Easy Enhancements Of Continuous Pin And Post Terminals", which was presented at the Connector And Interconnection Technology Symposium on Oct. 15-18, 1989 in Philadelphia, Pa., and which was published in its 1989 Annual Proceedings, whose contents also are herein incorporated by reference, which provides more detailed descriptions of the fabrication of such pins and various ways of using them, including the use of known pin systems with high speed pin insertion machines from reeled strips of the pins. The common methods for forming such pin strips is by coining, a cold-working process which upsets the material to form the enlarged diameter section.
The known pin configurations exhibit several deficiencies, including: providing the enlarged diameter section offers less retention than desired, increasing the widest dimension to improve retention often results in a loss of pin strength, provision of the enlarged diameter section often results in undesired axial enlargement of the pin, and the known enlarged diameter section manufacture cannot be applied to a continuous pin strip or used to make pins with non-round cross-sections or used to make miniature-sized pins.